The present invention relates to printing machines which are switchable between a single-side printing mode and a two-side printing mode in general, and more particularly to such printing machines in which the sheet being printed upon is turned during the operation in the two-side printing mode in accordance with the principle of trailing sheet edge turning.
In printing machines which are selectively operatable in the single-side printing mode and in the two-side printing mode, also sometimes referred to as a recto printing mode and recto and verso printing mode, the sheet being printed upon is engaged, while operating in the two-side printing mode, by a first gripper system of a sheet guiding or turning cylinder from a preceding cylinder at the tangential zone or nip of such cylinders at the trailing end of the sheet, is transferred to a second gripper system which swings in synchronism with the first gripper system, and then advanced further with the original trailing end forward. During the operation in the single-side printing mode, the sheet is engaged at its leading edge by the second gripper system of the sheet guideing ing or turning cylinder at the aforementioned tangential zone or nip, and then advanced further with its leading edge forward.
In order to enable the gripper systems of the sheet guiding or turning cylinder to engage the sheet being printed upon in one instance at the trailing end of the sheet and in the other instance at the leading edge of the sheet, it is necessary to perform the following adjustment steps during the switching between the two printing modes, that is, during the switching from the two-side printing mode to the single-side printing mode and vice versa:
gripper control (G)
adjustment of the angular positions of the control cams for the control of the movements of the second gripper system of the sheet guiding or turning cylinder, and of the gripper system of the cylinder arranged ahead of the sheet guiding or turning cylinder, in one sense or in the opposite sense, so as to assure an engagement and a release of the sheet being printed upon at different points in time as required by the different operating sequences during the printing in the single-side mode on the one hand, and in the two-side mode, on the other hand. A gripper control device for the centralized positional adjustment of the cams for controlling the gripper systems is known from the German Democratic Republic Pat. No. 155889.
ring gear (Z)
equalization of the phase shift between the part of the machine located upstream of the sheet guiding or turning cylinder and the machine part arranged downstream of such cylinder, in order to assure the engagement of the sheet being printed upon in one instance at the original trailing edge of the sheet and in the other instance at the original leading edge of the sheet. A ring gear control device for the equalization of the phase shift, including the performance of the operating steps of releasing a double gear, angularly displacing the gears and thus the machine parts relative to one another, and reestablishment of the connection of the double gear, is known from the German Democratic Republic Pat. No. 154082.
turning cylinder or drum (S)
release or arresting of the swinging motion of the first and of the second gripper system of the sheet turning cylinder or drum, in order to assure the sheet turning during the operation in the two-side printing mode, or the further transport of the sheet without turning during the operation in the single-side printing mode, as well as the adjustment of a guiding arrangement and selectively rendering a suction control device operative and inoperative, so long as the printing machine achieves the sheet turning by utilizing suction devices. A turning drum control device for the control of the swinging motion of the gripper systems from the operation in the single-side printing mode to the operation in the two-side printing mode, and vice versa, as well as for the performance of the other adjustment operations, is known from the Federal Republic Germany published patent application DE-OS No. 33 31 328.
initial position (A)
certain servicing operations can be accomplished only in certain initial positions of the printing machine. Up to now, the movement of the machine into such initial positions was accomplished by the operating personnel in accordance with the instructions contained in an operation manual.
If the printing machine is switched from the single-side printing mode to the two-side printing mode, and the format of the sheets to be printed upon is to be changed, it is necessary to perform the following operating steps:
achievement of an initial position PA1 ring gear adjustment. PA1 releasing the ring gear, PA1 angularly displacing the ring gear, and PA1 engaging the ring gear; PA1 releasing the ring gear, PA1 angularly displacing the ring gear, and PA1 engaging the ring gear, PA1 releasing the ring gear, PA1 angularly displacing the ring gear, and PA1 engaging the ring gear.
Herein, it is disadvantageous that, as a result of the differences in the successions of the operating steps during the switching from the single-side printing mode to the two-side printing mode, on the one hand, and from the two-side printing mode to the single-side printing mode, on the other hand as well as during the format changing operation, and as a result of the fact that certain adjustment operations can be performed only in certain initial positions of the printing machine and certain adjustment operations make it necessary to perform machine movements which are possible only when the elements to be adjusted are in certain positions thereof, the switching between the different printing modes is a difficult, time-consuming, and attention-requiring operation which, upto now, was accomplishable only manually. Obviously, lack of attention on the part of the operating personnel during the switching operation invariably results in machine damage.